<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
  <style>
    div{width: 100px;height: 100px;border: 1px solid red}
    #d1{
      /*单独某一个方向添加外边距*/
      margin-top: 50px;
      margin-left: 30px;
      margin-bottom: 50px;
      margin-right: 50px;
      margin: 30px;/*四个方向赋值*/
      margin: 50px 100px;/*上下和左右赋值*/
      margin: 10px 20px 30px 40px;/*上右下左顺时针赋值*/
    }
    #d2{
        /*兄弟元素上下相邻彼此添加外边距,取最大值(外边距塌陷导致)*/
        margin-top: 20px;
    }
    /*左右相邻彼此添加外边距,两者相加*/
    #s1{margin-right: 50px}
    #s2{margin-left: 50px;}
    #big{
        width: 200px;height: 200px;
        background-color: green;
        border: none;
        overflow: hidden;/*解决外边距塌陷导致的粘连问题*/
    }
    #big>div{
        width: 50px;height: 50px;
        background-color: blue;
        border: 0;
        margin-left: 50px;
        /*当元素的上边缘和上级元素上边缘重叠时,存在外边距塌陷问题,导致粘连在一起*/
        margin-top: 50px;
    }
  </style>
</head>
<body>
<div id="big">
    <div></div>
</div>
<span id="s1">span1</span><span id="s2">span2</span>
<div id="d1">div1</div>
<div id="d2">div2</div>
</body>
</html>